Growth of Cadmium Telluride Under Controlled Heat Transfer Conditions PDF Download
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Author: August F. Witt
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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The thrust of this research project was directed at the development of new approaches leading to growth of CdTe single crystals with improved crystalline and chemical perfection. In pursuit of this objective a theoretical analysis was made of the stability of the growth interface as a function of crystallographic orientation. Using the concept of dangling bond densities, it was found that experimentally observed solitary and lamellar twinning phenomena during growth can be directly related to anisotropy in the energetics of unavoidably curved crystal melt interfaces. The theoretical results obtained led to the development of a vertical Bridgman growth configuration in which heat transfer control is accomplished through an axially aligned heat exchange system comprising a heat pipe, a gradient control zone, and a heat levelling device. As an alternate approach to melt growth of CdTe, the suitability of the high pressure liquid encapsulation Czochralski technique (HP-LEC) was investigated. In the course of this study, analytical techniques, including IR transmission microscopy with image processing and absorption spectroscopy of the optical band edge, were developed and applied to investigations of the bulk defect structure. The results obtained during this research program constitute the basis for extensive DARPA, Air Force, and NASA sponsored research on growth of III-V and II-VI compound semiconductor systems.
Author: August F. Witt
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Book Description
The thrust of this research project was directed at the development of new approaches leading to growth of CdTe single crystals with improved crystalline and chemical perfection. In pursuit of this objective a theoretical analysis was made of the stability of the growth interface as a function of crystallographic orientation. Using the concept of dangling bond densities, it was found that experimentally observed solitary and lamellar twinning phenomena during growth can be directly related to anisotropy in the energetics of unavoidably curved crystal melt interfaces. The theoretical results obtained led to the development of a vertical Bridgman growth configuration in which heat transfer control is accomplished through an axially aligned heat exchange system comprising a heat pipe, a gradient control zone, and a heat levelling device. As an alternate approach to melt growth of CdTe, the suitability of the high pressure liquid encapsulation Czochralski technique (HP-LEC) was investigated. In the course of this study, analytical techniques, including IR transmission microscopy with image processing and absorption spectroscopy of the optical band edge, were developed and applied to investigations of the bulk defect structure. The results obtained during this research program constitute the basis for extensive DARPA, Air Force, and NASA sponsored research on growth of III-V and II-VI compound semiconductor systems.
Author:
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Category : Aeronautics
Languages : en
Pages : 440
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Author:
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ISBN:
Category : Military research
Languages : en
Pages : 644
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Author: Arun Pandy
Publisher:
ISBN:
Category :
Languages : en
Pages : 762
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Author: United States. Army Research Office
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 284
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Book Description
Vols. for 1977- consist of two parts: Chemistry, biological sciences, engineering sciences, metallurgy and materials science (issued in the spring); and Physics, electronics, mathematics, geosciences (issued in the fall).
Author: Lisa San Lun
Publisher:
ISBN:
Category :
Languages : en
Pages : 488
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Author: Jordan Douglas Roszmann
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Category :
Languages : en
Pages :
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The semiconducting compounds CdTe and CdZnTe have important applications in high-energy radiation detectors and as substrates for infrared devices. The materials offer large band gaps, high resistivity, and excellent charge transport properties; however all of these properties rely on very precise control of the material composition. Growing bulk crystals by the travelling heater method (THM) offers excellent compositional control and fewer defects compared to gradient freezing, but it is also much slower and more expensive. A particular challenge is the current need to grow new crystals onto existing seeds of similar size and quality. Simulations and experiments are used in this work to investigate the feasibility of growing these materials by THM without the use of large seed crystals. A new fixed-grid, multiphase finite element model was developed based on the level set method and used to calculate the mass transport regime and interface shapes inside the growth ampoule. The diffusivity of CdTe in liquid tellurium was measured through dissolution experiments, which also served to validate the model. Simulations of tapered THM growth find conditions similar to untapered growth with interface shapes that are sensitive to strong thermosolutal convection. Favourable growth conditions are achievable only if convection can be controlled. In preliminary experiments, tapered GaSb crystals were successfully grown by THM and large CdTe grains were produced by gradient freezing. Beginning with this seed material, 25 mm diameter CdTe and CdZnTe crystals were grown on 10 mm diameter seeds, and 65 mm diameter CdTe on 25 mm seeds. Unseeded THM growth was also investigated, as well as ampoule rotation and a range of thermal conditions and ampoule surface coatings. Outward growth beyond one or two centimeters was achieved only at small diameters and included secondary grains and twin defects; however, limited outward growth of larger seeds and agreement between experimental and numerical results suggest that tapered growth may be achievable in the future. This would require active temperature control at the base of the crystal and reduction of convection through thermal design or by rotation of the ampoule or applied magnetic fields.
Author:
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ISBN:
Category : Science
Languages : en
Pages : 1002
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Author:
Publisher: Newnes
ISBN: 0080932282
Category : Science
Languages : en
Pages : 3572
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Book Description
Semiconductors are at the heart of modern living. Almost everything we do, be it work, travel, communication, or entertainment, all depend on some feature of semiconductor technology. Comprehensive Semiconductor Science and Technology, Six Volume Set captures the breadth of this important field, and presents it in a single source to the large audience who study, make, and exploit semiconductors. Previous attempts at this achievement have been abbreviated, and have omitted important topics. Written and Edited by a truly international team of experts, this work delivers an objective yet cohesive global review of the semiconductor world. The work is divided into three sections. The first section is concerned with the fundamental physics of semiconductors, showing how the electronic features and the lattice dynamics change drastically when systems vary from bulk to a low-dimensional structure and further to a nanometer size. Throughout this section there is an emphasis on the full understanding of the underlying physics. The second section deals largely with the transformation of the conceptual framework of solid state physics into devices and systems which require the growth of extremely high purity, nearly defect-free bulk and epitaxial materials. The last section is devoted to exploitation of the knowledge described in the previous sections to highlight the spectrum of devices we see all around us. Provides a comprehensive global picture of the semiconductor world Each of the work's three sections presents a complete description of one aspect of the whole Written and Edited by a truly international team of experts
Author:
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Category : Power resources
Languages : en
Pages : 660
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